Trip interlock for static trip circuit breakers

ABSTRACT

A static trip unit is comprised of a current transformer module and an electronic programmer module physically and electrically mated together for incorporation in a molded case industrial circuit breaker. Current transformer modules and programmer modules are separately interchangeable to change breaker current ratings and functional capabilities. A trip interlock is included to prevent breaker closure in the absence of either the trip unit or the trip solenoid.

BACKGROUND OF THE INVENTION

The present invention relates to automatic molded case industrialcircuit breakers and particularly to such circuit breakers having staticor solid state trip units instead of the traditional thermal-magnetictrip units.

Electronic solid state trip units are increasingly being implemented inindustrial circuit breakers in place of the traditional thermal andmagnetic trip units to initiate circuit interruption automatically inresponse to an abnormal current condition in a protected load circuit.The increasing popularity of static trip units is largely due to theirinherent versatility and rather precise repeatability of selectedtrip-time response characteristics. That is, a circuit breaker statictrip unit can be designed to accommodate a wide range of user selectedresponse characteristics calculated to establish a highly repeatabletrip-time curve rather precisely tailored to a particular load so as toafford a full measure of overcurrent protection ranging from lightoverload to heavy short circuit proportions. Another attractive aspectof static trip units is that they can be readily and economicallysupplemented to also afford ground fault protection for a load circuit.In fact, the extreme versatility of modern static trip units presents apotential customer for an industrial circuit breaker with numerousoptions, i.e., functions, analogous to what one faces when buying a newautomobile.

In applicants' commonly assigned, copending application entitled "StaticTrip Unit for Molded Case Circuit Breakers" Ser. No. 130,321, filedconcurrently herewith, there is disclosed and claimed a static unitassembled from interchangeable current transformer and electronicprogrammer modules. This modularization of the major trip unitcomponents accommodates trip unit assembly and installation into acircuit breaker at the distributor level, thus significantly expeditingcustomer service. Moreover, circuit breakers in the field can be readilyconverted and serviced by interchanging one or both of these modules.Obviously, it is critically important that both trip unit modules bepresent, properly assembled and correctly installed, if the circuitbreaker is to perform its assigned circuit protective functions. Equallycritical is the necessity that the trip solenoid be properly installedto act in tripping its circuit breaker in response to trip signalsissued by the trip unit.

It is accordingly an object of the present invention to provide a tripinterlock for utilization in a static trip industrial circuit breaker.

A further object is to provide a molded case industrial circuit breakerincluding a removable static trip unit and having a trip interlockoperable to abort resetting of the circuit breaker in the event thestatic trip unit is not properly installed.

Yet another object is to provide a static trip circuit breaker of theabove character, wherein the trip interlock further operates to abortcircuit breaker resetting in the event the requisite trip solenoid isnot installed in the circuit breaker.

An additional object is to provide a static trip circuit breaker of theabove character wherein the trip interlock also operates to defeatcircuit breaker resetting if the trip solenoid is not properlyelectrically connected with the static trip unit.

Still another object is to provide a trip interlock of the abovecharacter which is efficient in construction and reliable in operation.

Other objects of the invention will in part be obvious and in partappear hereinafter.

SUMMARY OF THE INVENTION

In accordance with the present invention, there is provided a tripinterlock operable to guarantee the physical presence of both aremovable static trip and a trip solenoid within the molded case of anindustrial circuit breaker before closure of the breaker contacts can beeffected. The trip interlock also insures that the requisite electricalconnection between the trip unit and the solenoid is made before thecircuit breaker can be put into service.

In the illustrated embodiment, the static trip unit is comprised of acurrent transformer module and an electronic programmer module. Thecurrent transformer module consists of a plurality of individual currenttransformers, one for each breaker pole, each having a closed magneticcore embracing a conductive load strap constituting a single turnprimary winding. Wound on each core is a multi-turn transformersecondary winding. The current transformers are secured in spaced,side-by-side relation to the underside of an insulative support orhousing which also serves to mount a circuit board in positionimmediately above the transverse array of current transformers. Theterminations of the transformer secondary windings are brought out forelectrical connection to various terminal points on the circuit board.

The programmer module includes an insulative housing in which is mounteda second circuit board carrying the electronic components, includingintegrated circuit components, necessary to perform the requisite statictrip unit functions. Upon assembly of the programmer module to thecurrent transformer module, electrical connectors carried by therespective circuit boards are mated, such that the transformer secondarywindings are electrically connected to the programmer.

The assembled trip unit is then placed in a transversely elongatedcavity provided in the molded base of the circuit breaker case inintersecting relation with the breaker pole chambers adjacent the loadends thereof. The load straps are respectively electrically connected inseries with the individual pole circuits of the circuit breaker, suchelectrical connections also serving to physically secure the trip unitin place. Means are provided with the static trip unit for locating themounted positions of the trip solenoid and a circuit breaker latchmechanism within the breaker molded case. Included with the latchmechanism is a trip interlock member which is normally biased to a latchdefeat or tripping position effective in disabling the latch mechanismfor sustaining the breaker operating mechanism in its reset condition.Included with the trip unit is a receptacle into which a plugelectrically terminating the trip solenoid energizing coil is insertedto electrically connect the energizing coil into the programmer signalprocessing circuitry. This plug carries an activating protrusion which,while the plug is inserted in the receptacle, is in position to deflectthe interlock member out of its latch defeat position, thereby enablingthe latch mechanism to sustain the breaker operating mechanism in itsreset position. Consequently, absent the trip unit or the trip solenoidor the failure to insert the trip solenoid plug in the trip unitreceptacle, the trip interlock member assumes its latch defeat positionto prevent subsequent closure of the breaker contacts. Thus the circuitbreaker can not be put into service should these critical components beinadvertently omitted or the electrical connection therebetween beinadvertently neglected.

The invention accordingly comprises the features of construction andarrangement of parts which will be exemplified in the constructionhereinafter set forth, and the scope of the invention will be indicatedin the claims.

For a better understanding of the nature and objects of the invention,reference should be had to the following detailed description taken inconjunction with the accompanying drawings, in which:

FIG. 1 is a perspective view of an industrial molded case circuitbreaker incorporating the trip interlock of the present invention;

FIG. 2 is a side elevational view, partially broken away, of the circuitbreaker of FIG. 1;

FIG. 3 is a plan view, partially broken away, of the circuit breaker ofFIG. 1;

FIG. 4 is an exploded assembly view of the static trip unit removed fromthe circuit breaker of FIG. 1;

FIG. 5 is a perspective view of the trip interlock actuator utilized inthe circuit breaker of FIG. 1 as the interlock interface between acircuit breaker latch mechanism, a trip solenoid and the static tripunit;

FIG. 6 is a front view of the latch mechanism utilized in the circuitbreaker of FIG. 1;

FIG. 7 is a sectional view of the latch mechanism taken along line 7--7of FIG. 6, seen in its latching or untripped condition;

FIG. 8 is a sectional view of the latch mechanism taken along line 7--7of FIG. 6, seen in its unlatched or tripped condition;

FIG. 9 is a fragmentary, exploded, perspective view of the latchmechanism of FIG. 6, illustrating the latch defeat or trip interlockcomponents thereof;

FIG. 10 is a right side elevational view, partially broken away, of thelatch mechanism of FIG. 6, seen in its latch defeated condition;

FIG. 11 is a fragmentary, right side elevational view of the latchmechanism of FIG. 6, seen in its latching or untripped condition; and

FIG. 12 is a fragmentary right side elevational view of the latchmechanism of FIG. 6, seen in its response to a trip function initiatedby the static trip unit via the trip solenoid.

Corresponding reference numerals refer to like parts throughout theseveral views of the drawings.

DETAILED DESCRIPTION

A three-pole, static trip circuit breaker, generally indicated at 20 inFIG. 1, is seen to include a molded case consisting of a base 22 and acover 24 removably secured together by suitable means, such as screws25. An operating handle 26 protrudes through a centrally located opening24a in the cover front wall to accommodate manual operation of thebreaker between its open and closed conditions. Adjacent the lower orload end of the breaker a transversely elongated window 24b is providedin the cover to expose the upper end surface of a static trip unit,generally indicated at 28. A window pane 30, normally secured by screws31 in closure relation with window 24b, is removed to access controlknobs 32 for adjusting the response characteristics of the static tripunit.

As seen in FIG. 2, the internal circuit for each breaker pole includes,in series, a line lug 34 secured in electrical connection with outer endof a line strap 35 which mounts at its inner end a stationary contact36. A movable arm 37 carries adjacent its free end a movable contact 38for engagement with the stationary contact to conduct current throughthe arm and a flexible braid 39 to a conductive pad 40. An invertedU-shaped load strap 41 has its inner end portion in overlapping relationwith pad 40 and its outer end portion in overlapping relation with theouter end portion of a metal support pad 42 which is secured to thefloor 22a of base 22 by screws 42a. The inner end portion of the loadstrap is clamped in electrical connection with pad 40 by a bolt 43threaded into the tapped bore of an insert 43a anchored in the floor 22aof the base. One or more screws 44 are threaded into tapped holes insupport pad 42 to clamp a load lug 45 in electrical connection with theouter end portion of load strap 41, completing the internal seriescircuit for one breaker pole.

It is understood that the above-mentioned parts are duplicated in eachbreaker pole to provide, in the illustrated embodiment, three parallel,electrically isolated breaker pole circuits. The three movable contactarms 37 are ganged together by a crossbar 46 for concerted movementbetween open and closed circuit positions by a suitable operatingmechanism, such as a spring powered toggle mechanism as disclosed inJencks et al U.S. Pat. No. 3,053,954. This operating mechanism includesa cradle or trigger 47 which is releaseably held in a reset or untrippedposition by a latch mechanism, generally indicated at 48 in FIG. 2, soas to effect closure of the breaker contacts by handle 26. As best seenin FIG. 3, the latch mechanism includes a transversely elongated tripbar 50 which is impacted by the plunger 52a of a trip solenoid 52 uponpulsing of its coil under the control of static trip unit 28 pursuant toinitiating a trip function automatically in response to an abnormalphase current condition. The solenoid plunger tripping impact inducesswinging movement of the trip bar effective in conditioning latchmechanism 48 to release cradle 47, whereupon the breaker operatingmechanism springs (not shown) discharge to abruptly swing movablecontact arms 38 to their open circuit position. Tripping of the circuitbreaker may also be precipitated manually by depression of a trippushbutton 54 mounted by the cover as seen in FIGS. 1 and 2. The lowerconical tip of the pushbutton engages trip bar 50 to induce therequisite, trip initiating swinging movement thereof.

As seen in FIG. 4, load straps 41 in the three breaker poles are partsof the static trip unit assembly, and thus the electrical jointseffected by bolts 43 and 44 seen in FIG. 2 also serve to positionallysecure the trip unit in base 22 of the breaker molded case. Actuallyeach load strap is part of a separate current transformer subassembly,generally indicated at 56 in FIG. 4 and including a generallyrectangular magnetic core 58 embracing its associated load strap and inturn embraced at locations above and below the load strap by a pair ofbobbins 60. Each bobbin carries a multi-turn winding 62, with the twowindings electrically connected in series to provide a single currenttransformer secondary winding of the desired number of turns. Each loadstrap constitutes a single-turn primary winding carrying the phasecurrent for the breaker pole in which it is electrically connected.

The current transformer sub-assemblies are part of a current transformermodule, generally indicated at 64 in FIG. 4. This module includes anopen rectangular support structure or housing 66 formed of moldedinsulative plastic material. The current transformer subassemblies 56are nested into the open underside of housing 66 in side-by-siderelation and secured in place by screws 67 extending through holes 41ain the load straps and threaded into preformed holes (not shown) in thehousing wall. Seated on a perimetrical ledge (not shown) recessed fromthe upper edges of the housing sidewalls is a printed circuit board 68having terminal points or pads to which the terminations of the threecurrent transformer secondary winding 62 are electrically connected.This circuit board may also be provided with conductor runs andcomponents mounted to its underside for implementing a crowbarringcircuit automatically effective in dissipating dangerously highsecondary voltage levels induced in secondary windings 62. As anadditional feature, housing is provided with a pair of rearwardlyextending projections 66a accommodating terminal strips 69 havingpronged inner ends 69a rigidly solder connected to circuit boardterminal pads. The outer ends of these terminal strips are equipped withbinding head terminal screws 70 facilitating the electrical connectioninto circuit board 68 of the terminations of the secondary winding foran external neutral current transformer (not shown) when the static tripunit is designed to provide ground fault protection for a three phaseload circuit including a neutral conductor. These terminal screws alsoserve to secure circuit board in place. Terminal strips 69 are concealedby cover 24 when secured in closure relation with base 22. Molded intohousing 66 are partitions and depending barriers 66b serving to provideinterphase isolation between adjacent current transformer sub-assemblies56.

Completing the static trip unit assembly is a programmer module,generally indicated at 72 in FIG. 4. This module includes a shallowrectangular support structure or housing 74 formed of molded insulativeplastic. Captured within the open bottom of this housing is anotherprinted circuit board 76 which carries conductor runs, discretecomponents, integrated circuit chips, etc., making up signal processingcircuitry for performing the various circuit protective functions calledfor. The upper wall of housing 74 is suitably apertured, as indicated at74a, to accommodate the protrusion of the control shafts for variousswitches 77 mounted by circuit board 76. The exposed upper ends of theseshafts carry the control knobs 32 seen in FIG. 1. Also carried bycircuit board 76 are a plurality of depending male pin connectors 78which mate with female pin connectors 79 when programmer module 72 isseated atop current transformer module 64. The currents developed in thevarious current transformer secondary windings 62 by the phase currentsflowing through load straps 41 are routed by circuit board 68 and themated pin connectors 78, 79 to the programmer circuit board 76. Thesesecondary currents provide operating power for the programmerelectronics and signals indicative of the phase current magnitudes whichare processed by the programmer electronics pursuant to determining ifand when a trip function is to be initiated. The assembly of theprogrammer and current transformer modules is secured by screws 80passing through clearance holes in programmer module housing 74 andthreaded into preformed bores in current transformer module housing 66.Molded with the latter housing is an upstanding projection 66c which,upon assembly of the two modules, is received in a notch 74b formed inprogrammer module housing 74. The flat upper surface of this projectionis flush with the upper surface 74 and receives a label 32a seen in FIG.1, identifying a current rating for the current transformers asdetermined by their turns ratio. This current rating corresponds to thecontinuous current rating of the circuit breaker and establishes thecurrent magnitude factor to which the adjustable programmer currentsettings are calibrated.

From the description thus far, it is seen that by modularizing statictrip unit 28 into separate programmer and current transformer moduleswhich themselves are readily interchangeable, manufacturing and stockingeconomies are achieved. Thus, a circuit breaker can be economicallyproduced on essentially a shop order basis taking from stock the currenttransformer module having the current rating specified by the customerand the programmer module having the specified functional capabilities,assembling the modules into a static trip unit, and then installing thetrip unit in the breaker molded case. In fact, these operations may beperformed at various distributor locations, rather than at a singlefactory location. Moreover, current transformer modules may beinterchanged to change a particular breaker's continuous current ratingwithin the limits of its frame size. Programmer modules may beinterchanged to add or subtract functions, such as ground faultprotection, short time pickup and delay, fault indication, etc.Economies in field servicing are also achieved since, in all likelihood,only one of the two trip unit modules need be replaced to rectify anytrip unit field problem.

Trip solenoid 52, seen in FIG. 3, has its energizing coil terminationsbrought out via wires 82 to a plug connector 84 seen in FIGS. 4 and 5.This plug connector is slidingly received in a socket or receptable 74cmolded into programmer module housing 74. Wires 82 are terminated inseparate female pin connectors for electrical engagement with a pair ofupstanding male pin connectors 86 carried by programmer circuit board 76as the plug connector is slid downwardly into receptacle 74c. The tripsolenoid is thus wired into the programmer, ready to initiate a tripfunction in response to a trip signal pulse generated by the programmerelectronics. The connected position of plug 84 in recess 74c isreleasably sustained by a resilient hook 88 (FIG. 5) molded intoprogrammer module housing 74.

To facilitate positional mounting of the trip solenoid in one outsidepole of the circuit breaker, a pin 90 (FIG. 4) is press-fitted in a holeprovided in the load strap 41 stationed in that breaker pole. A bracket91 (FIG. 3), supporting the trip solenoid, is provided with a dependingflange 92 (FIG. 4) having a hole 92a into which pin 90 is inserted topositionally locate the free end of plunger 52a in confronting relationwith trip bar 50. A bolt 93 (FIG. 3) projecting through a hole in alaterally turned flange 91a of bracket 91 and threaded into the breakerbase, serves to secure the operational position of the trip solenoid. Asseen in FIG. 4, the other outside pole load strap may also be equippedwith a pin 90 serving to positionally locate a shunt trip orundervoltage release solenoid accessory (not shown) in this breaker polein the same manner as the trip solenoid 52 in the other outside pole.The accessory solenoid plunger would also act on the trip bar 50 to tripthe circuit breaker.

Latch mechanism 48, seen in FIGS. 2 and 3, will now be described ingreater detail in conjunction with FIGS. 6 through 12. Thus the latchmechanism includes a supporting frame 100 (FIGS. 6, 9 and 10) having aback wall 100a, opposed sidewalls 100b and a bottom wall 100c. Bolts102, extending through holes in the frame backwall, are threaded intotapped holes 103 (FIG. 4) provided in the center pole load strap 41.Also, bolt 43, making the electrical joint between the center pole loadstrap 41 and center pole conductive pad 40, extends through a hole inthe frame bottom wall, thereby fixedly securing the latch mechanism inplace in the center pole region of the circuit breaker. A primary latch104 is pivotally and slidably mounted by a transverse pin 106 mounted bythe frame sidewalls 100b. Torsion springs 108 bias the primary latchboth rightwardly and in the clockwise direction, as viewed in FIGS. 7and 8, into position to latchably engage the tip of cradle 47 (FIG. 2)pursuant to retaining the breaker operating mechanism in its resetcondition. Counterclockwise torque exerted on the primary latch by theoperating mechanism springs is normally resisted by a roller pin 110carried by a secondary latch 112 pivotally mounted by a pin 113 carriedby latch mechanism frame 100. The resulting counterclockwise torqueexerted on the secondary latch is normally resisted by a transverselatch pin 114 rotatably mounted between the frame sidewalls. Morespecifically, as seen in FIG. 7, the upper tip 112a of the secondarylatch normally engages the periphery of the latch pin at a longitudinallocation aligned with a notch 114a formed therein. It is thus seen thatwhen the latch pin is rotated in the counterclockwise direction, thesecondary latch tip 112a rides off the latch pin periphery into thespace left by notch 114a. The secondary latch is thus unlatched and freeto pivot in the counterclockwise direction. The unlatching restraintimposed on the primary latch by the secondary latch roller pin 110 isthus removed, and the primary latch is freed to pivot in thecounterclockwise direction. Cradle 47 is thus released to swing in theclockwise direction viewed in FIG. 2, and the circuit breaker is trippedto effect abrupt separation of the breaker contacts.

Trip bar 50 is mounted by a bail 120 pivotally mounted adjacent its endsby screws 122 threaded into the frame sidewalls 100b, as seen in FIG. 6.This bail, also seen in FIGS. 9 through 12, is biased in thecounterclockwise direction by a torsion spring 124 to a quiescentposition determined by the abutment of a bail mounted tab 126 against astop 127 (FIGS. 6 and 11) carried by frame 100. Also mounted by bail 120is a depending trip tab 128 (FIGS. 9, 11 and 12) positioned inconfronting relation with the upper end of a trip pin 130 radiallymounted by latch pin 114 adjacent its right end as seen in FIG. 6.

From the foregoing description, it is seen that when the trip solenoidcoil is pulsed by a trip signal generated by the programmer, its plnger52a (FIG. 3) springs out into tripping impact with trip bus 50. Asviewed in FIGS. 11 and 12, bail 120 is thus pivoted in the clockwisedirection, swinging trip tab 128 rightwardly to pick up the upper end ofa trip pin 130 and induce an increment of clockwise rotation of latchpin 114 sufficient to unlatch secondary latch 114 (FIGS. 7 and 8) andprecipitates tripping of the circuit breaker.

It will be appreciated that should the circuit breaker 20 be put intoservice without either programmer module 72 or trip solenoid 52 inplace, its ability to provide any form of circuit protection is lost.Absent the programmer module, there is no means to process the currenttransformer secondary signals. On the other hand, if the trip solenoidis absent or not wired into the programmer module electronics, there isno means to act in response to programmer generated trip signals. Toguard against the potentially hazardous consequences attending theinadvertent failure to install these components, a trip interlock lever134 is journalled on bushing 100d carried by the right frame sidewall100b as best seen in FIG. 9. A torsion spring 136, carried by a pin 138mounted by the right frame sidewall, has its one end 136a hooked on thelower end of trip pin 130 and its other end 136b acting on the lower endof trip interlock lever 134, as best seen in FIGS. 11 and 12. Acting onthe upper end of the trip interlock lever is a nose 140 which isintegrally molded with the body of plug connector 84 (FIG. 5.). However,if either the programmer module or the trip solenoid, or both are notinstalled, or they are both installed but the plug connection wiring thetrip solenoid into the programmer electronics has not been made, nose140 is obviously absent. This situation is depicted in FIG. 10. Spring136 rotates trip interlock lever 134 in the clockwise direction, andthis motion is communicated to latch pin 114 by the engagement of a hubshoulder 134a of the interlock lever with trip pin 130. The latch pin isthus angularly oriented to its tripping position seen in FIG. 8.Consequently, all restraints against counterclockwise pivotal movementof primary latch 104 are moved, and it is incapable of sustaining cradle47 in its reset position. Thus, the breaker operating mechanism can notbe reset, a prerequisite to subsequent closure of the breaker contacts.

On the other hand, when plug connector 84 is fully inserted intoreceptacle 74c provided in programmer module housing 74 to electricallyconnect the trip solenoid with the programmer electronics, conditionsseen in FIGS. 11 and 12 are achieved. Specifically, nose 140 of the plugconnector engages the upper tip of the trip interlock lever to rotatethis lever in the counterclockwise direction. This motion is coupled tolatch pin 114 by spring 136, which is then rotated in thecounterclockwise direction to its latching angular position seen in FIG.7. The secondary latch tip 112a then engages the latch pin periphery,enabling the primary latch to hold the cradle in its reset position whenthe breaker operating mechanism is manually reset by handle 26.

It will thus be seen that the objects set forth above, among those madeapparent in the preceding description, are efficiently attained and,since certain changes may be made in the above construction withoutdeparting from the scope of the invention, it is intended that allmatter contained in the above description or shown in the accompaningdrawings shall be interpreted as illustrative and not in a limitingsense.

Having described my invention, what I claim as new and desire to secureby Letters Patent is:
 1. In combination with a molded case industrialcircuit breaker having a latch mechanism for releaseably sustaining abreaker movable contact operating mechanism in its reset conditionrequisite to subsequent breaker contact closure, a static trip unitremovably mounted with the breaker molded case, and a trip solenoidseparately removably mounted within the breaker molded case in positionto induce, in response to electrical activation of its energizing coilunder the control of the trip unit, tripping action of the latchmechanism pursuant to releasing the breaker operating mechanism from itsreset condition and thereby produce abrupt breaker contact opening, atrip interlock comprising, in combination:A. an electrical receptaclecarried by the trip unit and electrically connected into signalprocessing circuitry of the trip unit; B. a plug electricallyterminating the energizing coil of the trip solenoid, said plug beinginserted into said receptacle to electrically connect the energizingcoil into the signal processing circuitry; C. a trip interlock memberincluded in the latch mechanism, said member normally biased to a latchdefeat position disabling the latch mechanism from sustaining thebreaker operating mechanism in its reset condition; and D. a tripinterlock actuator carried by said plug, with said plug inserted in saidreceptacle, said actuator assuming a position of engagement with saidtrip interlock member effective in displacing same from its latch defeatposition and thereby enabling the latch mechanism to sustain the breakeroperating mechanism in its reset condition.
 2. The trip interlockdefined in claim 1, wherein said receptacle is in the form of a socketrecessed in a portion of a housing for the static trip unit.
 3. The tripinterlock defined in claim 2, wherein said receptacle further includesdetent means formed with the trip unit housing portion for releaseably,engageably detaining said plug in said receptacle.
 4. The trip interlockdefined in claim 1, wherein said trip interlock actuator consists of aprotuberance formed on the body of said plug.
 5. The trip interlockdefined in claim 1, wherein said trip interlock member is mounted by thelatch mechanism for pivotal movement into and away from its latch defeatposition, said member coupled with a latch element of the latchmechanism such as to urge the latch element to a trip precipitatingposition upon being biased to its latch defeat position, said tripinterlock further including spring means biasing said trip interlockmember to its latch defeat position and biasing the latch element fromits trip precipitating position to a latching position enabling thelatch mechanism to sustain the reset condition of the breaker operatingcondition when said trip interlock actuator displaces said tripinterlock member from its latch defeat position.
 6. The trip interlockdefined in claim 4, wherein said receptacle is in the form of a socketrecessed in a portion of a housing for the static trip unit.
 7. The tripinterlock defined in claim 6, wherein said receptacle further includesdetent means formed with the trip unit housing portion for releasably,engageable detaining said plug in said receptacle.
 8. The trip interlockdefined in claim 7, wherein said trip interlock member is mounted by thelatch mechanism for pivotal movement into and away from its latch defeatposition, said memeber coupled with a latch element of the latchmechanism such as to urge the latch element to a trip precipitatingposition upon being biased to its latch defeat position, said tripinterlock further including spring means biasing said trip interlockmember to its latch defeat position and biasing the latch element fromits trip precipitating position to a latching position enabling thelatch mechanism to sustain the reset condition of the breaker operatingcondition when said trip interlock actuator displaces said tripinterlock member from its latch defeat position.
 9. In combination witha molded case industrial circuit breaker having a latch mechanism forreleaseably sustaining a breaker movable contact operating mechanism inits reset condition requisite to subsequent breaker contact closure, astatic trip unit removably mounted with the breaker molded case, and atrip solenoid separately removably mounted within the breaker moldedcase in position to induce, in response to electrical activation of itsenergizing coil, tripping action of the latch mechanism pursuant toreleasing the breaker operating mechanism from its reset condition andthereby produce abrupt breaker contact opening, a trip interlockcomprising, in combination:A. an electronic programmer module removablyincorporated in the trip unit as an essential functional componentthereof, said programmer module including an electrical receptacleelectrically connected into signal processing circuitry thereof; B. aplug electrically terminating the energizing coil of the trip solenoid,said plug being inserted into said receptacle to electrically connectthe energizing coil into said programmer module signal processingcircuitry; C. a trip interlock member included in the latch mechanism,said member normally biased to a latch defeat position disabling thelatch mechanism from sustaining the breaker operating mechanism in itsreset condition; and D. a trip interlock actuator carried by said plug,whereby, with said plug inserted in said receptacle, said actuator,assuming a position of engagement with said trip interlock membereffective in displacing same from its latch defeat position and therebyenabling the latch mechanism to sustain the breaker operating mechanismin its reset condition.